Purification of resistance protein complexes using a biotinylated affinity (HPB) tag.

Plant disease resistance (R) proteins confer strong resistance against pathogens by recognizing particular pathogen effectors. Identification of proteins associated with an R protein will provide insight into the mechanism of R protein function. Many R proteins are associated with the plasma membrane (PM) and expressed at low levels. Here, we describe a method to purify such low-abundance PM R protein -complexes from Arabidopsis using a biotinylated affinity tag, called the HPB tag. We have successfully applied this method to identify candidate components of the RPS2 resistance protein complex(es). This method should also be applicable to purification of other low-abundance PM protein complexes.